Review: Digital Fortress

Dan Brown is famous as the author of The Da Vinci Code. One of his earlier efforts was Digital Fortress (available online here) a book about the NSA and codebreaking. Now, I don't mind it when writers who, when dealing with complex real-life topics, sometimes play a little fast-and-loose with the nitty-gritty details. After all, this is fiction, right? Sometimes changing details serves to improve the story. Sometimes it only matters that the author gets the broad picture across, because only geeks care about the minutiae. Well, in this novel Brown fails to get anything right; the plot is weak and contrived, the characters are ludicrous, the broad picture is incomprehensible and, yes, he gets the crypto details completely wrong.

Fortunately for me, I have a twisted sense of humour. I enjoyed reading this, solely because of the old "it's so bad it's good" thing.

So. This is a lazy review. Summary: the novel is bad, and very bad if you're crypto-savvy. Here are some choice quotes as evidence:

• If Susan’s body had been lanky and awkward as a teenager, it sure wasn’t now. Somewhere along the way, she had developed a willowy grace—slender and tall with full, firm breasts and a perfectly flat abdomen. David often joked that she was the first swimsuit model he’d ever met with a doctorate in applied mathematics and number theory.
  
• “Exactly. An algorithm that resists brute force will never become obsolete, no matter how powerful code-breaking computers get. It could become a world standard overnight.”
  Susan pulled in a long breath. “God help us,” she whispered.
  
• Enigma was history’s most famous code-writing machine—the Nazis’ twelve-ton encryption beast. It had encrypted in blocks of four. (The real Enigma weighed 12 kg - ed.)
  
• Encryption algorithms were just mathematical formulas, recipes for scrambling text into code. Mathematicians and programmers created new algorithms every day. There were hundreds of them on the market—PGP, Diffie-Hellman, ZIP, IDEA, El Gamal. TRANSLTR broke all of their codes every day, no problem. To TRANSLTR all codes looked identical, regardless of which algorithm wrote them. (and to Dan Brown, software, compression methods, key-agreement algorithms, public-key encryption schemes and block ciphers all seem identical - ed.)
  “I don’t understand,” she argued. “We’re not talking about reverse-engineering some complex function, we’re talking brute force. PGP, Lucifer, DSA—it doesn’t matter. The algorithm generates a key it thinks is secure, and TRANSLTR keeps guessing until it finds it.”
• Caesar, she explained, was the first code-writer in history. When his foot-messengers started getting ambushed and his secret communiqués stolen, he devised a rudimentary way to encrypt this directives. He rearranged the text of his messages such that the correspondence looked senseless. Of course, it was not. Each message always had a letter-count that was a perfect square—sixteen, twenty-five, one hundred—depending on how much Caesar needed to say. He secretly informed his officers that when a random message arrived, they should transcribe the text into a square grid. If they did, and read top-to-bottom, a secret message would magically appear. (Brown's just described a columnar transposition cipher. I know it's a subtle point, but Caesar actually invented what's confusingly known as the Caesar cipher, a simple substitution cipher - ed.)
  Over time Caesar’s concept of rearranging text was adopted by others and modified to become more difficult to break. The pinnacle of non computer-based encryption came during World War II. The Nazis built a baffling encryption machine named Enigma. The device resembled an old-fashioned typewriter with brass interlocking rotors that revolved in intricate ways and shuffled cleartext into confounding arrays of seemingly senseless character groupings. (It seems the only type of encryption Brown understands is transposition, but sadly none of the systems he names were transposition schemes. The Enigma didn't "shuffle cleartext", nor did the Caesar cipher. Most importantly, the rotors were made chiefly from rubber or bauxite, not brass. OK, OK, I'm nitpicking now... -ed.)
  

There's more, but I don't want to spoil them for you ;-)

Tags: Cryptography , Encryption , Digital Fortress